iio: adc: qcom-spmi-adc5: add an unique irq name

Currently, interrupts of qcom-spmi-adc5 driver are registered
with name "pm-adc5". However on platforms with multiple PMICs
that can have different ADC types (adc5 or adc7), this naming
is not user friendly when looking at interrupt data. Add a name
that looks unique for different adc types so that they can be
interpreted easily.

Change-Id: Iac1080dc8e02d278b30cff0d61eca40e081bc306
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>